I was curious if anyone else desired a parallelism to +: in pattern matching that mimics what's available for Lists (::). If you're like me, feel free to borrow the code, but also speak up! I'll find out about adding it into the standard library.

Note: We could also have a matching :+ operator for (x.init, x.last) decomposition as well. (Only really efficient for IndexedSeq, I would guess).